RU2362123C2 - Flow rate metre - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: proposed metre comprises the casing made up of two parts 1,6, delivery nozzle 2, nozzle 3 to deliver measured medium into casing inlet hole 5 and outlet branch pipe 30. Casing chambers 9 and 10, separated by shutter 7 and membrane 8, are filled with measured and tested media (the latter representing fluid with known density, i.e. water, spirit, ether). Membranes 11, 12 with positive floatability bodies 22 and 23 fastened thereon, separate appropriate chambers into above-membrane spaces 13, 14 and below-membrane spaces 15 and 16. Casing channels 19, 20, communicating below-membrane spaces and space 4 between the nozzles, accommodate sealing elements 28, 29 representing pistons rigidly fixed on previously mentioned positive-floatability bodies. Channels 19, 20 are integrated with two differential-transformer membrane displacement convertors 24, 25 connected with analog-digital 31, in its turn, connected with single-chip microcontroller 32. Magnetoconducting solid body or nonwettable magnetic fluid makes the core of convertors 24, 25.

EFFECT: higher accuracy and expanded performances.

3 cl, 4 dwg

Description

The invention relates to measuring equipment and is intended to measure flow with increased accuracy while measuring density and determining the composition (ratio of components in the mixture) of the pumped two-component liquid, for example rocket or aviation fuel, oil products, a mixture of water and oil in conditions of large temperature extremes, for example changes in flight altitude, with periodic alternation of the illuminated (sunny) and shadow sides with sharp changes in temperature, in various climatic conditions ovia.

A known flow meter comprising a housing consisting of two parts and including a supply and a guide nozzle, a receiving hole made in the partition of the housing, an elastic sensitive element, such as a membrane, an outlet pipe and a transducer for moving the elastic sensitive element into an output signal, the cavity between the nozzles communicating with submembrane cavity of the body (AS USSR No. 533824, IPC G01F 1/34, 10.30.1976).

The closest in technical essence and the achieved result to the claimed device is a flow meter containing a housing consisting of two parts and including a supply and a directing nozzle, a receiving hole made in the baffle of the housing, an elastic sensitive element, for example a membrane, an outlet pipe and an elastic sensitive displacement transducer element into the output signal, and the cavity between the nozzles communicated with the submembrane cavity of the housing. An additional body with positive buoyancy, rigidly fixed to the sensitive element (AS USSR No. 1174754, IPC G01F 1/34, 08.23.1985) was additionally introduced into it.

The disadvantage of these flowmeters is the error caused by the dependence of the output signal taken from the membrane displacement transducer on the density of the medium being measured, the inability to determine the density of the measured liquid, and in a two-component liquid (for example, oil and water), the ratio between the components of the mixture can change over time, which in turn leads to a change in the density of the liquid.

The objective of the invention is to increase the accuracy of measurement and expand the functionality of the flowmeter, which consists in additionally determining the density of the liquid, as well as the ratio between the components in a two-component mixture.

The problem is achieved in that in a flowmeter containing a body consisting of two parts and including a supply nozzle and a nozzle directing the jet of the medium to be measured into a receiving hole made in the body, a membrane with a positive buoyancy body separating the body chamber filled with the medium to be measured into two cavities - a submembrane and submembrane communicating with the cavity between the nozzles, the outlet pipe and the differential transformer transducer displacement of the elastic sensing element in the output signal al, unlike the prototype, an additional chamber is made in the flowmeter body, divided by a second membrane with a body of positive buoyancy into two cavities - a membrane and a submembrane, filled with a test medium - water, alcohol, ether or another test liquid with a known density, the chamber chambers are separated by a partition and membrane, the submembrane cavity of the additional chamber is connected by a channel containing the membrane with the cavity between the nozzles, into the channels connecting the submembrane cavities of the housing chambers and the cavity between the nozzles and, two sealing elements are introduced, while the channels are combined with two differential transformer transducers of displacements of the membranes of cameras with moving cores, the transducers are connected to an analog-to-digital system, which is connected to a single-chip microcontroller.

In addition, a magnetically conductive solid body or non-wettable magnetic fluid placed in the connecting channels is used as the cores of the differential transformer displacement transducers.

In addition, the sealing elements are made in the form of pistons rigidly fixed to bodies of positive buoyancy.

The invention is illustrated by drawings. Figure 1 shows a schematic diagram of a flow meter, figure 2 - the forces acting on the body of positive buoyancy, explaining the principle of operation of the flow meter, figure 3 presents graphs of the dependence of the readings of the flow on the density for the developed structure and for its prototype, and Fig. 4 illustrates the dependence of the percentage composition of a two-component fluid on the density of this fluid.

The design of the device of the invention comprises a housing 1, a supply nozzle 2, a guide nozzle 3 installed coaxially with a gap. A supply nozzle 2 forms a cavity 4, while a guide nozzle is installed with a gap against a hole 5 made in the upper part 6 of the housing 1. The internal volume of the housing 1 is divided by a partition 7 and a membrane 8 into two chambers 9 and 10, which, in turn, are divided by membranes 11, 12 into two parts, which form the supmembrane cavities 13 and 14 and the submembrane cavities 15 and 16, respectively. Cavities 15 and 16 are connected by channels 17, 18, 19 and 20 with cavity 4.

At the outlet of the connecting channel 18, a membrane 21 is in front of the cavity 16. Bodies with positive buoyancy 22 and 23 are fixed on the membranes 11 and 12, respectively. The supmembrane cavity 14 and the submembrane cavity 16 of the chamber 10 are filled with a test fluid with a known density, for example water or test oil. On channels 19 and 20 there are two differential transformer displacement sensors (DTP) 24 and 25, the movable cores (26 and 27) of which are placed in channels 19 and 20. Non-wettable magnetized liquid can be used as cores. In the channels 19 and 20, sealing elements 28 and 29 are also placed, for example, pistons located in the channels 19 and 20, respectively, with a rod rigidly fixed to the body with positive buoyancy 22 or 23, respectively. The fluid outlet is through the outlet pipe 30 located in the housing 1. The differential transformer displacement sensors 24 and 25 are connected to an analog-digital system 31, for example, BIS K572PV4, which is connected to a single-chip microcontroller 32, for example K1816BE51.

The flow meter operates as follows. Formed by the supply nozzle 2, the jet of the measured medium is directed through the guide nozzle 3 into the hole 5, fills the internal cavity 13 with liquid, acts on it and flows through the pipe 30 in the body 1 of the flow meter. In this case, the cavity 13 perceives both static pressure and high-speed jet pressure, which is proportional to the square of the medium flow rate and its density.

where R _ST - hydrostatic pressure;

R _D - hydrodynamic pressure;

P ₁₃ - pressure in the cavity 13.

where ρ _and is the density of the measured fluid;

Q is the volumetric flow rate;

υ is the flow rate in the guide nozzle 3;

S ₃ - the area of the holes of the guide nozzle 3.

Due to the fact that the jet flowing out of the nozzle 2, initially retaining its cylindrical shape, becomes conical before it enters the hole of the guide nozzle 3, low pressure is created in the cavity 4, since the flow between the outlets and inlets of the nozzles 2 and 3 has a large kinetic energy in this region and therefore low potential energy.

where P ₄ is the pressure in the cavity 4;

To ₄ - the coefficient of pressure perception cavity 4.

Due to this, the pressure coming from the cavity 4 through the connecting channels 17 and 18 in the cavity 15 and 16 is slightly lower than the static pressure. The membrane 21 is located at the outlet of the connecting channel 18 in front of the cavity 16, ensuring equal pressures in the cavities 4 and 16, as well as sealing the cavity 16 from the cavity 4, preventing mixing of the measured and test fluid. The membrane 8 transfers pressure from the cavity 13 to the cavity 14, which is filled with a test medium.

Thus, membranes 11 and 12 with positive buoyancy bodies 22 and 23 are under the action of a force due to the pressure difference in the supmembrane and submembrane cavities, and buoyancy force (Archimedes force) proportional to the density of the liquid and the volume of the body with positive buoyancy 22 or 23, respectively. Under the action of these forces, the membrane 11 with the body fixed on it with positive buoyancy 22, located in the chamber 9, filled with the measured medium, moves up or down.

where P ₁₁ is the pressure perceived by the membrane 11 located in the cavity 9;

P ₁₂ is the pressure perceived by the membrane 12 located in the cavity 10;

P ₄ - pressure in the cavity 4;

P _A1 is the pressure of the Archimedes force, perceived by the membrane 11 of the chamber 9;

P _A2 is the pressure of the Archimedes force, perceived by the membrane 12 of the chamber 10; P _G - gravity pressure on the membranes 11 and 12.

where V is the volume of bodies with positive buoyancy 22 and 23;

S ₁₁ and S ₁₂ - the area of the membranes 11 and 12;

ρ _t is the density of the test medium in the chamber 10;

ρ _p - the density of bodies with positive buoyancy 22 and 23.

As can be seen from the above formulas (5) and (6), if the pressure caused by the Archimedes force acting on the body of positive buoyancy 22 exceeds the hydrodynamic pressure and the pressure caused by gravity acting on the body of positive buoyancy 22, then the membrane 11 moves up if the pressure caused by the Archimedes force acting on the body of positive buoyancy 22 is less than the sum of the hydrodynamic pressure and the pressure due to gravity, then the membrane moves down. Similarly, for the membrane 12 with a positive buoyancy body fixed on it, located in the chamber 10 filled with the test medium. Since the pressures of the above- and submembrane 13, 15 chambers 9 are the same as the pressures above and below the membranes 14, 16 of the chamber 10 filled with test fluid, and therefore the positions of the membranes themselves do not coincide due to the fact that since the chambers 9 and 10 are filled with liquids with different densities (a measured medium with a variable unknown density and a test medium with a predetermined density), and therefore with different Archimedes forces (P _A1 and P _A2 ) acting on bodies with positive buoyancy 22 and 23.

Taking into account (5 and 6), the equilibrium equation for bodies with positive buoyancy 22 and 23 will have the form:

where F ₁₁ is the elastic force of the membrane 11;

F _A22 - Archimedes force acting on a body of positive buoyancy 22;

F ₁₃ - the force of the hydrodynamic pressure of the liquid;

F ₄ - the pressure force of the fluid in the cavity 15 (corresponding to the pressure in the cavity 4) on the membrane 22;

F _G22 - body gravity of positive buoyancy 22.

For camera 10, the equation takes the following form:

where F ₁₂ is the elastic force of the membrane 12;

F _A23 - Archimedes force acting on a body of positive buoyancy 23;

F ₁₄ - the force of the hydrodynamic pressure of the liquid;

F ₄ - the pressure force of the fluid in the web 15 (corresponding to the pressure in the cavity 4) on the membrane 22;

F _G23 - body gravity of positive buoyancy 23.

The action of forces on the membranes 11, 12 with positive buoyancy bodies 22, 23 fixed to them is shown in FIG. Since the membranes 11 and 12 are absolutely identical, the forces of gravity acting on them will be equal, i.e. F _G23 = F _G22 . Since the pressures in the supmembrane chambers 13 and 14 are equal and also equal to the area of the membranes 11 and 12, the forces of the hydrodynamic pressure of the fluid in the supranembrane chambers on the membranes 11 and 12 will be equal, i.e. F ₁₄ = F ₁₅ . From this we can conclude that in equations (10) and (11) only Archimedes forces acting on the bodies of positive buoyancy 22 and 23 (F _A22 and F _A23 ) will be different, which will depend on the density of the liquid into which the bodies of positive buoyancy are immersed (measured fluid in chamber 9, and test fluid in chamber 10).

where F _A23 is the force of Archimedes acting on the body of positive buoyancy 22/23;

ρ _{and / t} - density of the measured medium / test fluid;

V _22/23 - body volume with positive buoyancy 22/23.

The gravity of bodies with positive buoyancy 22, 23 is determined by the following formula:

where F _G22 / F _G22 is the force of gravity acting on the body of positive buoyancy 22/23.

The elastic forces of the membranes 11 and 12 (F ₁₁ / F ₁₂ ) will depend on the rigidity of the membranes and the displacement of the membranes:

where F _11/12 is the elastic force of the membrane 11/12;

C is the rigidity of the membranes 11 and 12, and since the membranes 11 and 12 are identical, the rigidity for the membranes 11 and 12 will be equal;

X _11/12 - displacement of the membrane 11/12.

Given the formula (3), the force of the hydrodynamic pressure of the fluid (F ₁₃ ) and the force of the fluid pressure in the cavity 15 (corresponding to the pressure in the cavity 4) on the membrane 22 (F ₄ ), can be represented in the following form:

where S ₁₁ is the area of the membranes 11, 12;

P ₄ - pressure in the cavity 4;

P ₁₃ - pressure in the cavity 13;

Q is the volume of the measured fluid;

S ₃ - the area of the holes of the guide nozzle 3.

In accordance with the above, formulas (10) and (11) can be represented as follows:

where X _11/12 is the displacement of the membrane 11/12;

P ₄ - pressure in the cavity 4;

V ₂₂ is the volume of bodies with positive buoyancy 22 and 23.

From (17) it follows that the difference in the displacement of the membranes 11 and 12 depends on the difference in the density of the measured liquid and the test medium.

Since the density of the test fluid (ρ _t ) and the volume of bodies with positive buoyancy 22 and 23 (V ₂₂ ) are known, then, by measuring the difference in the mixing of the membranes, it is possible to determine the density of the measured fluid. The sealing elements 28 and 29 are used to transfer the displacement of the membranes 11 and 12 into the channels 19 and 20, as well as isolating these channels from the submembrane cavities 15 and 16. The sealing elements 28 and 29 may be pistons located in the channels 19 and 20, with a rod, rigidly fixed to the body with positive buoyancy 22 or 23, respectively. Therefore, the displacement of the membrane 11 is transmitted through the channel 19 to the movable core 26 of the differential transformer transducer 24 of the chamber 9. The membrane 12, located in the chamber 10 filled with the test medium with the same pressures as the chamber 9, biases the core 27 of the differential transformer transducer 25 of the chamber 10 The displacement of the core 27 is measured by differential transformer transducers 25, which provide signals functionally related to the flow rate and the density of the liquid in the chamber.

where U ₂₄ and U ₂₅ are the voltages taken from the differential transformer converters 24 and 25, respectively;

X ₁₁ X ₁₂ - displacement of the membranes 11, 12;

K ₂₄ = K ₂₅ - conversion factors for differential transformer converters 24 and 25, respectively.

Since the chamber 10 is filled with a test medium whose density is known, the signal of the differential transformer transducer 25 of the chamber 10 is proportional to the flow without error caused by the unknown density of the measured medium, and the difference between the signal values of the differential transformer transducers 24 and 25 will be proportional to the density of the measured medium.

As follows from formulas (19) and (20), as well as the equality of the conversion coefficients (K ₂₄ = K ₂₅ ) for the differential transformer converter 24 and 25, formula 21 can be represented as follows:

where F _A22 / F _A23 - Archimedes force acting on bodies with positive buoyancy 22/23.

Using the formula (12), we obtain:

The analog-digital system 31 converts the analog signals from the differential transformer converters 24 and 25 into a parallel digital code that goes to a single-chip microcontroller 32, where in accordance with the value of these signals and the oil density of a given well, the flow rate (26) and density (24) are calculated measured liquid, as well as the percentage of oil-containing liquid in it (25).

The density of the measured fluid is found by the following formula:

Knowing the density, you can determine the composition of the liquid:

where µ ₁ and µ ₂ are the percentage composition for water and oil liquids, respectively;

ρ _n = Const is the density of the oil-containing fluid for this well, stored in the ROM of the microcontroller.

where gV / S ₁₁ = Const and ρ _n = Const; ρ _p - body density of positive buoyancy;

ρ _and is the density of the measured fluid, determined by (24);

K ₂₄ - conversion coefficient for the differential transformer Converter 24, is stored in the ROM of the microcontroller;

U ₂₄ - the voltage taken from the differential transformer Converter 24, is supplied to the MC with the ADC.

As can be seen from formula (26), the error in measuring the flow rate caused by the variable density, in contrast to the prototype, is taken into account, which significantly increases the accuracy of the measurement. On the graph shown in figure 3, simulated the readings of the flow meter and its prototype depending on the density of the measured fluid. As can be seen from the graph, the developed flowmeter has a slight error caused by the fact that the pressure in the cavity 4 is slightly less than hydrostatic, while the prototype, in addition to this error, has a more significant deviation from the real value, caused by the dependence of the hydrodynamic pressure, which is measured to obtain the flow value , from the density of the measured liquid (P _D = ρ _and Q ² / 2S ₃ ² ). The graph presented in figure 4 shows the dependence of the percentage composition (µ ₁ and µ ₂ ) of a two-component liquid in water and an oil-containing liquid on the density of this liquid measured by the developed device. For example, with the density of the measured liquid ρ _and = 850 kg / m ³ , for oil with the density ρ _n = 800 kg / m ³ , the percentage composition of the liquid will be as follows: μ ₁ = 25% - the percentage composition of water, μ ₂ = 75% - percentage of oil in a given bicomponent fluid.

Thus, the flow meter improves the accuracy of flow measurement by compensating for the error caused by the variable density of the medium being measured, and allows you to further determine the composition of the liquid by its density.

Claims (3)

1. A flowmeter comprising a body consisting of two parts and including a supply nozzle and a nozzle directing the measured medium stream into a receiving hole made in the body, a membrane with a positive buoyancy body, dividing the body chamber filled with the measured medium into two cavities - a membrane and a submembrane, communicating with the cavity between the nozzles, the outlet pipe and the differential transformer transducer displacement of the elastic sensing element in the output signal, characterized in that in the housing flow the measure made an additional chamber, divided by a second membrane with a body of positive buoyancy into two cavities: a submembrane and a submembrane filled with a test medium - water, alcohol, ether or another test fluid with a known density, the body chambers are separated by a partition and a membrane, the submembrane cavity of the additional chamber is connected by a channel containing a membrane with a cavity between the nozzles, two sealing elements are introduced into the channels connecting the submembrane cavities of the body chambers and the cavity between the nozzles, This channel is combined with two differential transformer transducers of displacements of the membranes of cameras with moving cores, the converters are connected to an analog-to-digital system, which is connected to a single-chip microcontroller. 2. The flow meter according to claim 1, characterized in that the cores of the differential transformer displacement transducers used a magnetically conductive solid or non-wettable magnetic fluid placed in the connecting channels. 3. The flow meter according to claim 2, characterized in that the sealing elements are made in the form of pistons rigidly fixed to bodies of positive buoyancy.

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